1. Field of the Invention
This invention relates to rotary wood chippers for reducing wood materials into chips and more particularly to an improved seal in such apparatus.
2. Description of the Prior Art
In tree trimming or removal operations, limbs and other scrap wood material must be disposed of, which in the past has been accomplished by burning the scrap wood. In populated areas, such burning increases the pollution content of the air which is undesirable. Recently, the scraps have been reduced to wood chips which can then be employed for paper manufacture or, in some cases, used as a mulch around shrubs and the like. It is not generally feasible, however, to truck the wood scraps to a mill for processing in wood chippers since the expense of the gathering and shipping frequently outweighs the value of the resulting wood chips.
Some wood chippers have been designed which are portable and which are capable of processing at least small branches into wood chips which then can be gathered at the site of the tree trimming operation or can be distributed on the ground whereupon the chips will decay naturally without causing environmental pollution. Some existing portable wood chippers, however, are generally not capable of handling relatively large limbs or medium sized trees (i.e., with diameters up to 15 inches). This problem is due to the relatively lightweight construction of the trailer-hauled portable wood chippers which are designed primarily for very small branches and not general duty purposes. On the other hand, existing wood chippers which are designed for larger pieces of wood material are extremely heavy and cannot easily be transported; or in cases where heavy duty chippers have been mounted on large trailers, the cost of the unit is prohibitive for small operators. Thus, there existed a need for a relatively heavy duty and yet portable chipper unit which was not overly costly.
U.S. Pat. No. 3,844,489 disclosed on improved wood chipper comprising a generally rectangular chipping block having at least one aperture extending through the block and a chipper knife positioned on the edge of the aperture. Positioned on flat top and bottom edges of the rectangular block are chip clearing fan blades. The chipping block is enclosed and rotatably mounted in a housing which has an input aperture on one face for receiving material to be chipped and a discharge chute extending tangentially from the periphery thereof for removal of wood chips. The housing is mounted on a suitable framework at an acute angle relative to the direction of feed such that the chipper knife tends to draw the material into the chipper. Rotation of the chipping block is facilitated by a rotary shaft mounted between a pair of bearing block assemblies bolted to the outside of the housing. The bearing assemblies are of conventional design.
A considerable amount of air is generated inside the housing to discharge the wood chips. Because the housing together with the shaft is at an acute angle to a horizontal plane and due to the air currents which pull the chips from the housing, the upper bearing assembly is kept relatively free from dirt and other contaminants. However, the lower bearing assembly tends to accumulate dirt such that the seals can fail and thereby expose the lower bearings to contamination. Consequently, the lower bearings tend to fail prematurely.